Sotto Voce Chest Voice

It is seldom that a fine artist is heard to use the falsetto register, except it be at the beginning or end of a crescendo or diminuendo.

Although falsetto tones gain some strength by practice, still they always remain weak and effeminate, and when used on continuous words, produce a contrast between the two registers which is exceedingly disagreeable to listen to. Most singers who use the falsetto voice in singing the high tones, are those who have impaired voices, or who, from lack of a proper method, have not the ability to sing the chest tones softly and in tune, hence resort to the falsetto tones as a substitute for the sotto voce chest voice. All the tones of the male voice, except it be at the beginning of the crescendo or the end of a diminuendo, should be in the chest register, and if the voice be properly educated, these tones will last as long as does the body; and the sotto voce or soft chest tones, will pass into the falsetto register without the slightest difficulty, producing the crescendo or diminuendo without a break. When the falsetto tone is used, care should be exercised to use the same quality as that of the chest tone.

—J. Harry Wheeler, Vocal Physiology, Vocal Culture and Singing (1883), page 51-52.

Wheeler was a student of Manuel García and Francesco Lamperti.